I'm playing in the Modern era on an archipelago map for the first time. Throughout the game I have been taking cities with my navy (G&K). My next enemy target has started building air units, and she uses frigates and privateers for her navy. My armada is made up of a large number of battleships, a privateer, a carrier with some aircraft, and ironclad coastal raiders for capturing.

I have not really used destroyers in any serious way before. I'm debating whether to spend a few more turns researching, and upgrade the ironclads to destroyers before I attack. Anyway, the question:

The destroyer has a special ability called "Interception (40)". Does this mean it has a 40% chance to intercept air attacks? Or does it always intercept, and have 40% bonus strength while intercepting? The Civilopedia and wikis are unclear about this. I also searched the internet and did not find a definitive answer.

I think that either way, it will probably be helpful to finish the tech and bring destroyers against this opponent. But I would use different positioning, and spend money upgrading different numbers and types of units, depending how the naval Interception ability works. Thanks in advance for insight!

The Intercept(X) ability gives X% chance to intercept aircraft within it's range (100% chance if it's the target of the attack).

I would probably upgrade to destroyers just because they will damage the fighters a lot more. They only get one interception per turn (even if attacked multiple times), but you'll take out some fighters over time. As Ironclads you'll lose more ships, since the fighters will get more attacks before they die.

Thanks! That thought about damage/unit Strength actually led me to try another course as an experiment. My opponent's harbor+Petra capital was in an amazing desert location, and my spies reported the capital and its neighbor were pumping out aircraft every second turn (!!). I decided since I was about 15 turns from researching Destroyers (eek!), to just try an attack with my large armada of battleships. I hid my ironclads behind them, out of range of the many Great War bombers.

Guess what the AI did! She placed three bombers on a carrier and moved them out of her city, into the range of ten or eleven battleships, I suppose to get at my ironclads 8+ tiles out from the city. (I wish I could have privateered that, to see if I'd steal the aircraft. My privateer had gotten distracted.) Well, that went straight to the ocean floor.

The rest of the enemy's Triplanes and Great War Bombers repeatedly blew themselves up trying to attack my battleships. They didn't do that much harm...I lost one low-level battleship which I felt was a good trade for this capital. The computer switched to building battleships itself after it finished its aircraft. I took the capital swiftly.

I think if the enemy had been building Bombers instead of Great War Bombers, I would have had lots of dead ironclads. I wouldn't want to see a regular Bomber hit one, because the Great War Bomber outright kills them, or nearly so.

While on the topic of interception--I suppose I have two more questions about it which I haven't yet demonstrated in G&K:

1. Can an aircraft set to intercept, do it more than once per turn? (I know the anti-air gun can only intercept once.)

2. Do multiple interceptors covering a tile, still all fire simultaneously at the first air-based attacker? (I remember that's what was happening last I played vanilla.)

I thought it was odd that the carrier came out of the city full of bombers. I know the AI is mentally deficient in war. But in G&K, more often than not, I see AI units retreat from me and go behind their city instead of coming out to die. (This of course makes capitals pretty easy to take now...) I don't know what I did to cause the carrier to come out into my battleships instead of retreat. (Perhaps it was "retreating" by hoping to float right through my navy...)